Electronic switch



Dec. 31, 1946.

J. F. FA RRINGTON ELECTRONIC SWITCH Filed May 15, 1942 2 Sheets-Sheet 1 llllllllll.lllllll q 019 on 3 G 03 @M mm nwwm mosh \llloErr I N N d w M/ z m H mm? m mm 0 EF. W W fwoc m 31 1946- J. F. FARRINGTON 2,413,440

ELECTRONIC SWITCH Filed May 15, 1942 2 Sheets-Sheet 2 e e Control Potermol Gon'rol Potential FIG. 2

INVENTOR ai W ATTORNEY uaung opouv'" Q Patcntcd Dec. 31, 1946 ELECTRONIC SWITCH John F. l arrlllttoll. Tilton, N H.,'assign r, by mesne asaignmcntntoflaleitine lzlno Chicago, 111., a corporation oi Illinois Application May 15,1942, Serial No. 443.11!

1: Claim. (Cl. 250-27) 1 The present invention relates to electronic switches and, particularly, to such switches of the multiunit or multistage type used selectively to couple one or more signal sources to one or more output circuits.

It is often desirable to provide an electronic switch by which any selected one of a plurality of signals may be coupled tq a translating circuit, or to translating circuits individual to such si nals, or in, which'one signal may be selectively coupled to any one of a plurality of translating circuits. While mechanical switches have been used for this purpose, an electronic switch has numerous advantages in many applications. Outstanding among these advantages are its substantially instantaneous operation, the fact that it is controllable by a potential alone and thus requires no appreciable consumption of power in its control circuit, its stable and positive action, and its freedom from the many troubles which characterize the use of electrical contacts necessarily used in mechanical switches.

It is frequently desirable that a multistage electronic swtich be provided with one control cir cuit by which selectivelyto control the several switching stages thereof. Where the electronic switch has a single control circuit for all stages. it is desirablethat each switching stage be positively, stably, and selectively controlled by individual values of a characteristic of a control signal or potential applied to the "control circuit. In order that the switch may be suitable for a wide variety of applications, it is desirable that the values of the control potential or signal which selectively control the switching stages thereof may occur in any desired order or may even occur in a random order as the circumstances of the particular application demand. It is further desirable that an electronic switch shall involve a minimum of circuit elements and apparatus, that it shall have a simple circuit arrangement, shall be inexpensive and adaptable to many and diverse applications, and that it shall be characterized by stable and reliable operation over long periods of use.

It is an object of the present invention, therefore, to provide a new and improved electronic switch of the type described.

It is a further object of the invention to provide a new and improved electronic switch which possesses one or more of the desirable features heretofore specified.

.It is an additional object of the invention to provide an electronic switch of the multistage type wherein the stages thereof may be selective- 2 ly controlled by individual'amplitude values of a control potential and one wherein such values of the control potential may occur in any random order as desired.

In accordance with the invention, an electronic switch comprises a plurality of vacuum-tube switching stages each including an output circuit at which a signal translated by the stage is developed. The conductance characteristics of the stages depend primarily on' the values of space. currents of the aforesaid vacuum tubes. The electronic switch includes a signal input circuit for each of the stages, and means for applying to each of the stages a signal input having an effective amplitude varying over a. predetermined amplitude range, at least a portion'of each of the signal input circuits being common to all of the stages. There is additionally included in the electronic switch means individual to the.

' amplitude range of the signal input, selectively to translate the portion of the signal input lying within the aforesaid portions of the amplitude range, the last-mentioned means in at least one of the stages including .means for rendering the one stage unresponsive to all amplitude values of the input signal different. from the aforesaid portion of the aforesaidamplitude range individual to the one of the stages.

In accordance with a particular form of the invention, an electronic switch comprises a plurality of vacuum-tube switching stages each including an input circuit having a circuit portion adapted to have applied thereto a signal and each including an output circuit at which the signal is developed after translation through the aforesaid each stage. The conductance characteristics of the stages depend primarily on the values of space currents of the vacuum tubes thereof. Another portion of the input circuits of the stages is common to all of the stages and is adapted to have applied thereto a control potential having selectively-variable amplitude values. The switch includes means individual to the stages for controlling the conductance characteristics thereall amplitude values of the ccntrol potential different from the aforesaid amplitude value individual to the one of the stages.

For a better understanding of the present invention, together with other and further objects thereof, reference is had to the following description taken in connection with the accompanyi drawing and its scope will be pointed out in the appended claims.

Referring now to the drawings, Fig. 1 is a circuit diagram, partly schematic, of a complete electronic switch embodying the invention; Figs. 2, 3, and 4 are graphs used as an aid in explaining the operation of the invention; and Figs. 5 and 6 are circuit-diagrams of electronic switches embodying modified forms of the invention. I

Referring more particularly to Fig. 1 of the drawings, there is represented a complete electronic switch embodying the present invention in an arrangement having numerous applications as will hereinafter be pointed out in greater detail. This electronic switch comprises several units; namely, an electronic switch unit per se, designated by the reference numeral II, a stepvoltage generating unit H, and a periodic-pulse generatingunit l2. Briefly considered, it is the purpose of the unit l2 to generate a periodic potential of pulse wave form which is applied to an input circuit of the generator H. The latter derives from this periodic potential another peri-' odic potential the amplitude values of which increase by successive steps during each period thereof. This step voltage is applied to a control circuit-oi the electronic-switching unit II to cause the switching stages thereof to be successively and periodically controlled, thereby successively to translate a plurality of signals, individually applied to the switching stages of this unit, to individual ones of a plurality of output circuits of the electronic switch.

Considering first the detailed circuit arrangement of the electronic switch Ill, this unit comprises a plurality of vacuum-tube switching stages l2-l'l, inclusive, only the detailed circuit arrangement of the stages l2 and I4 being shown for purposes of simplicity, it being understood that all of the stages "-11, inclusive, are similar and include similar circuit elements in a similar circuit arrangement. Each such switching st e includes a vacuum tube I. having a control electrode IS, a screen electrode 20, and an anode 2|. Each stage also includes an input circuit coupled to the control electrode l8. This input circuit has a circuit portion, comprising the input or control-voltage circuit terminals 22; 22 of theelectronic switch l0, common to all of the switching stages and has another circuit portion individual to each of the switching stages and adapted to have a-signal applied thereto. Such individual circuit portion of the input circuit comprises the cathode circuit of vacuum tube i2 and includes a. winding 24 and a source of operating bias comprising a battery 25 connected in series between the cathode of vacuum tube l8 and ground. There is coupled to the winding 24 a winding 26 which is connected to the input circuit terminals 21, 28 adapted to have applied thereto a signal which is to be translated through the switching stage associated therewith. Each of the switching stages also includes an output circuit comprising output circuit terminals 22, 22 to which the signal individual to each stage is applied after translation through each such stage.

The input or control circuit terminals 22, 22 of the electronic switch It are adapted to have applied thereto a control potential having selec- 4 tively-variable amplitude values. The electronic switch includes means individual to the switching stages thereof for controlling the conductance characteristic of each such stage to render each of the stages responsive only to at least. individual amplitude values of the controlpotential, selectively to translate the applied signals from the input circuit to the output circuit associated therewith. This means comprises a load imped- 1 ance or load resistor 2! of relatively high value, for example of the order of one-half to one me ohm, included in the output circuit of the vacuum tube ll between the anode 2! thereof and a source of space current indicated as +13. The last named means also comprises a. source of operating bias indicated as +Sc for the screen electrode 22 of vacuum tube IS, the relative value of the operating potential of screen electrode 20 being critically proportioned in a manner presently to be explained, and eflectively includes the battery 25 in the cathode circuit of the vacuum tube II, the voltage of this battery also having a critical value as will presently be apparent. In the event that it is desirable in some application to use the unit I. alone, provision must be made for completing a direct current path from the control electrode l9 to ground. This path normally will becompleted through the external control circuit which is connected to the control circuit terminals 22, 22, as in the arrangement of Fig. 1. However, where this is not the case, a resistor R, indicated in broken lines for the reason that it may be comprised in whole or in part by the resistance of the external control circuit, is connected across the control circuit terminals 22, 22.

The periodic-pulse generator I2 is of the conventional blocking-oscillator type and includes a vacuum tube 22 and a transformer 22 having a primary winding 24 included in the output circuit of the vacumn tube 22, and a secondary winding 2! included in the input circuit of this vacuum tube. The input circuit of tube 22 additionally includes a grid resistor 24, a grid condenser 21, and a resistor 22, the latterbeing connected in series with the transformer winding 25 and being coupled to a synchronizing-signal input circult comprising terminals 22, 44. A cathode resistor 4| is included in the output circuit of vacwave form developed across this resistor is applied through the output circuit terminals 42, 42

to the input circuit terminals 44, 45, respectively,

of the step-voltage generating unit ll. Unit l2 in the Fig. 1 arrangement may be used for several purposes; for example. to provide a periodic potential of pulse wave form which is necessary to derive the step potential generated by the unit It or,when the Fig. 1 arrangement is used as a counter system by which to count the number so of pulses in a synchronizing signal applied to its input circuit terminals 22, 42 of unit l2, this unit may be used as a frequency divider wherein the frequency of the periodic potential generated by \mit l2 will be a selected sub-multiple of the frequency of the periodic potential applied to its input circuit terminals 22, 42.

The step-voltage generator H includes a vacuum-tube repeater 42 having input electrodes coupled to the input circuit terminals 44, 45 of this unit and output electrodes coupled to a pair of rectifier devices 41, 42 which are connected in parallel with each other with opposite polarities.

There is included in circuit with the rectifier device 42 a condenser 42 across which the step voltage is derived. A second vacuum-tube reuum tube 22 and a periodic potential of pulse -cally to discharge the condenser 49 to reduce its voltage substantially to zero. There is provided in unit II for this purpose a transformer 54 having a winding 55 coupled across cathode resistor I and a secondary winding 55 which is coupled to the input electrodes of a vacuum tube 51. The control electrode of vacuum tube 51 is negatively biased from a source of potential 58. The anode and cathode .elements of vacuum tube 51 are connected directly across the condenser 49.

In considering the operation of the Fig. 1 arrangement, the operation of the electronic switch unit III will first be considered and reference will be made to the curves of Figs. 2 and 3 for that purpose. Considering specifically the operation of one of the switching stages, for example the stage I3, it has been found that when the operating bias applied to the screen electrode 20 of the vacuum tube I8 is maintained constant at a given value, the use of a large value of resistance for the load resis'tor 3| has the effect that, over a wide range of control potentials applied from the control circuit terminals 22, 23 to the control electrode I9 of tube I8, the anode current of this tube starts from anode current cutoff, determined by the value of voltage of battery 25, and increases rapidly to a value at which no further increase is experienced. characteristic is represented by curve A of Fig. 2. Anode current cutoff occurs when the control potential has any value less than e1, lesser values of potential being insuificient to overcome the bias of battery 25, and the anode current has a large constant value when the control potential has any value larger than e2. The fact that the anode current of tube I8 becomes constant for any value of the control potential larger than the value eg is due to two factors. The first of these relates to the large voltage drop which the anode current produces across the load resistor 3| by virtue of the large value of resistance of the latter with the result that little or no voltage is applied to the anode 2| of tube I8 when the anode current becomes large. The second factor relates to the fact that the screen electrode has applied thereto a positive potential having a relatively high and constant value with the result that as the anode potential decreases due to increasing magnitudes of the potential drop across the resistor 3I, the screen electrode tends to collect larger quantities of the electrons emitted by the cathode of tube I8 and ultimately collects completely any additional electrons emitted by the cathode. The particular value ez of the control potential which causes the anode current to become constant is thus determined both by the value of the load resistor 3| and by the value of the potential applied to the screen electrode 20.

It will be seen from curve A that the anode current of the vacuum tube- I8 changes over the range e1-ez of the control potential, that is, to

individual amplitude values thereof, but that the anode current has a relatively constant value for amplitude values of the control potential above this rangeand a substantially zero value for amplitude values below such range. Bearing in mind that the anode potential of tube I8 decreases with increasing values of its anode current due to the load resistor 3|, the slope of This anode current curve A at any given point cannot be used to give the exact value of transconductance of tube I8 at that point but is useful as an indication or measure of the transconductance. The brokenline curve B of Fig. 2 represents the manner in which the transconductance of the vacuum tube I3 varies with the control potential. It will be seen from curve B that the vacuum tube I8 has relatively high transconductance, and thus has a relatively high repeating ratio, at substantially one individual amplitude value es of the control potential and has relatively low transconductance for amplitude values substantially different therefrom.

The value of control potential at which the vacuum tube I8 has high transconductance may be varied over a wide range by proportioning the values of the biasing battery 25, the value of the operating bias applied to the screen electrode 20, and the value of resistance of the load resistor 3 I. In practice, these values are soproportioned that each of the switching stages I3-II, inclusive, has high transconductance only at one individual amplitude value of the control potential, as represented by the curves of Fig. 3, wherein the curves Al, A2, A3, A4, A5 represent the transconductance characteristic of the respective switchin stages I3-I'I, inclusive. Only the switching stage I3 is thus responsive to the zero amplitude value of the control potential and is effective for this value of the control potential to translate the signal applied to its input circuit terminals 21, 28 to its output circuit terminals 29, 30. When the control potential has the amplitude value e4, the switching stage I3 is no longer responsive to the control potential, and hence the signal individually applied thereto is not translated to its output circuit terminals 29, 30. On the other hand, the switching stage I4 is responsive to this value of the control potential and is effective to translate the signal applied to its input circuit terminals 21, 28 to its output circuit terminals 29, 30. In similar manner, the switching stages I5, I6 and I! are responsive to individual amplitude values e5, es and 5 ev, respectively, of the control potential selectively to translate the signals individually applied thereto from the input circuit to the output circuit associated therewith.

It will be evident that the individual amplitude values of the control potential at which the switching stages I3-I'I, inclusive, are responsive may occur in any random order. For example, if the control potential during a given interval has the successive amplitude values 0, e7, e5, e6, :24, the switching stagesare rendered responsive in the corresponding order I3, II, I5, I6 and I4. However, in the particular arrangement shown in Fig. 1, the switching stages I 3-I'I, inclusive, are adapted to be rendered successively operative by a control potential applied to the control circuit terminals 22, 23 of unit I0, from the unit I I, having amplitude values which increase by successive steps. The manner in which this step voltage is produced will now be considered.

Consider first the operation of the periodic-potential generator I2. In the absence of a potential applied to its synchronizing circuit terminals 39, 40, a periodic potential of pulse wave form, represented by curve C of Fig, 4, is developed across the cathode resistor 4| by a blocking-oscillator action well understood in the art. This operation, briefly, is as follows: Starting at the time when the anode current of vacuum tube 32 just begins to increase, a voltage is induced in the winding 35 of the transformer 33 which drives the grid. of vacuum when in a positive direction. The anode current thereupon increases yet'further with the result that a corresponding increase occurs in the positive potential applied to the control electrode. This action is cumulative until the anode current of vacuum tube 32 reaches a saturation value.

During the time when the anode current is thus increasing, the condenser 31 is charged by grid rectification. When the anode current of tube 32 reaches a constant .value, a voltage is no longer induced in the winding of thetransformer 33 and the charge of the condenser 31 is effective to place a large negative bias upon the control electrode of tube 32, whereby the latter is biased to anode current cutoff. This action occurs very quickly since decreasing values of anode current induce a, voltage in the winding 35 which drives the control electrode of tube 32 to an even higher negative potential. After a time interval, depending upon the time constant of condenser 31 and resistor 36, the charge leaks off of the condenser. 31, anode current again begins to flow in the vacuum tube 32, and the cycle previously described is repeated.

' The anode current of tube 32 flows through the cathode resistor 4| to develop thereacross the desired periodic potential. The period of this periodic potential is thus determined by the time constant of the condenser 31 and resistor 36 and may be made slightly longer than the period of a synchronizing signal applied to the input circuit terminals 39, 40, in order that the synchronizing signal may control in conventional manner the period of this potential, or may be made a multiple number of periods of the synchronizing signal, as desired. The periodic potential developed across the cathode resistor 4| is applied through the output circuit terminals 42, 43 to the input circuit terminals 44, 45 of the step-voltage generator I i.

The periodic potential pulses applied to the in put circuit terminals 44, 45 of unit II are repeated by the vacuum-tube repeater 46 thereof and are applied to the rectifier devices 41 and 48. The rectifier device 48 conducts during the positive portions of the periodic potential applied thereto to charge the condenser 49 by a finite value to produce for each pulse of the periodic potential one step of the desired step potential. The rectifier device 41 conducts during the negative portion of the applied periodic potential to preserve. at the rectifier devices 41 and 48 the electrical axis of the periodic potential.

The wave form of the desired step potential is represented by the curve D of Fig. 4 and it will be seen that the amplitude values of this voltage successively increase through a desired number of steps, for example five. At the end of the last such step, the potential across the condenser 49 must be reduced to zero. This is effected by the discharge vacuum tube 51 in the following manner The potential developed across ,the condenser 49 is repeated by the vacuum tube 50 to the cathode resistor 5| thereof and is also applied between to the anode and cathode of the discharge vacuum tube 51. Increases in *value of the step potential developed across the cathode resistor 5| of tube 50 are applied as small negative pulses through the transformer 54 to the control electrode of the vacuum tube 51, but have no effect since the. latter is biased by the battery 58 to a value such that tube 51 becomes conductive only when its anode potential, developed across the condenser 49, becomes slightly larger than the step of the step potential. Tube 81 upon becoming conductive starts to discharge the condenser 43 which, oi course, reduces the potential developed across cathode resistor Iii of tube 53. and causes a positive pulse to be applied through the transformer 54 to the 'control electrode of tube 31, thus tending to increase the anode current of tube 51 even more. This action is cumulative to drive the control electrode of tube I! so far positive that this tube has a very low value of conductance, thus causing tube 81 substantially instantly and completely to discharge the condenser 43. When this has occurred, the voltage developed across the cathode resistor SI of tube it assumes a steady-state value and no voltage is thereafter applied through the transformer 54 to the control electrode of vacuum tube 51. The latter thereupon again becomes nonoonductive'due to the bias applied to its control electrode from battery 33, and the cycle is repeated.

' The step potential thus developed across cathode resistor ii of vacuum tube 50 is applied through the output clrcuit'terminals 52, 53 of unit H to the input circuit or control circuit terminals 22, '23 of unit ill to cause the switching stages lJ-Ii, inclusive, thereof to become successively operative in the manner previously described.

While the units H), H, and i2 are shown in Fig. 1 as being interconnected, it will be evident that the switching unit l4 may be used alone, in which event a suitable control potential having selectively-variable amplitude values is applied to its control circuit terminals 22, 23 selectively to renderthe switching stages 13-, inclusive, operative .in the manner described. 0n the other hand, the units II and II may alone be used together as a counter system for counting the number of pulses, for example, of a periodicpulse potential applied to the input circuit terminals 44, 45 of the unit Ii. The units III, II

and I2 have a useful application as a counter 45 system for measuring the number of pulses of a periodic-pulse potential applied to the input circuit terminals 39, 43 of unit I2 and, when so used, the number of pulses indicated by the system may be the exact number of pulses of 50 the applied potential or a sub-multiple number thereof, as desired.

The foregoing description of the switching unit i0 may seem to indicate that the switching stages l3-I'I, inclusive, thereof can only be responsive 55 to such widely-spaced individual amplitude values of the control potential applied to the control circuit terminals 22, 23 .that there are values of the control potential at which all of the switch- .ing stages have substantially zero transconductance. However, this is not the case, for it will be evident that the circuit constants of the switching stages may be so adjusted and proportioned, if desired, that two or more of the switching stages have maximum response to the same given amplitude value of the control potential or, alternatively. two of the stages may have overlapping transconductance characteristics. Where two such stages have overlapping transconductance characteristics as last suggested, each will have maximum response to an individualamplitude value of the control potential, but both may have some partial response at intermediate values of the control potential. The latter arrangement may have a useful application. for example, in television systems where it value of the last desired tube I8, comprise means for individually fixedly biasing each of the stages 12-", inclusive,oi the electronic switch it to control a conductance characteristic thereof to render each of the stages onlyresponsive to at least individual amplitude" values of the control potential selectively 'to translate the applied signals from the input-circuit to the output circuit associated therewith.

That is,- these elements comprise means individual to the switching stages 13-41, inclusive. for imparting to each oi the stagesa relatively high transconductance when the control potential has 'at least individual amplitude Values and a relatively low transconductance for other amplitude values thereof to render each of the stages only responsive to individual amplitude values.

or the control potential.

Fig. represents a' circuit diagram of an electronic switch embodying a modified form of the invention which is essentially similar to the electronic switch ll of Fig. 1, similar circuit elements being designated by similar reference numerals and analogous circuit elements by similar reference numerals primed. While only three switching stages I 3', I 4', and ii are here shown,

it will be evident that other similar stages may be used if desired, as in the Fig. 1 arrangement. The present arrangement permits the use of thetriode type of vacuumtube It although this type of tube is not essential to the operation of the instant arrangement and a screen-grid type of tube may be used, if desired, as in the Fig. l arrangement, there being the difierence where the latter type of tube is used that the screengrid potential has a normal value and the load resistor 3.1 a normal value of resistance; that is, thesev circuit parameters need not be specially proportioned as in the Fig. l arrangement. The

" principal distinguishing feature between the Fig.

1 and Fig. 5 arrangements consists in the use of two resistors 80, 6| which are connected. inseries between the control electrode I! of the vacuum tube l8 and one control circuit terminal, for example the terminal 22, of the electronic switch It. The winding 24 of the input transformer Y 24, 28 of each of the switching stages is coupled through a condenser. 62 to the common junction of the resistors 60 and 8 I.

Considering now .the operation of the Fig. 5 arrangement, the switching stages l3, l4, and ii are initially adjusted for operation by choosinga value or potential of the bias battery 25' of each such thatithe' vacuum tube ll of each switching stage is normally biased on the linear portion of its operating characteristic at one individual amplitude value of the control potential appliedto the control circuit terminals 22, 23. Assume, for example, that the value of the control: potential at a given time is such that the algebraic sum of its-value and that'otthe batteryz25sof stage I3 is correct to operate thevacuum tube I 8' of this stage on the linear portions of itsoperating characteristic. This vac uum tube is thus eflective at this time to translate-the signal applied to its input circuit ter- '-I'= minals 21, 28.'to its output circuit terminals 29,

'30. :.-At the same time, however, this amplitude value of the vappliedcontrol potential is.insufli-.

the unit I. of

' 1o cient to cause the vacuum tubes of the switches ll and W togbe biased above anode current cutoff and hence; the latter stages are not eiie'ctive to-tnanslate the signals applied thereto to-their respective output circuits;

5 Now assume that the amplitude 01.

the I applied control, potential increases so that the algebraic sum .oLits value and'that'of the battery 25 ofthe switching stagei'il' is correct -to bias the, vacuum tube Rot the switching stage M. to. the linear portion of its characteristici ,The switching-stage l4 thereupon ,becomeseiiective to translate the signal ap lied to its .inpu circuit terminals 21, 28-to its output circuit-termiyet'insumcient to bias the vacuum tube of the switching stage. lS' -above anode current cutofl and-the latter is ineflective to repeat to its output circuit thesignal applied to its input circuit. At the. same time, however. this value of' control potential causes the control electrode I! of the vacuumtube l8'- of' switching stage ii to 3 become so positive that a. continuous current flows between this control electrode and the that the signal applied to the input circuit terminals 21, 28 01' the switching stage I3 produces a signal voltage of substantially the same am-.

plitude across the resistor SI of the stage and only a negligibly small portion or the signal volt- 'tage is applied to the control electrode IQ of the vacuum tube lc' of the stage. The switchin stage It is therefore. for all practical purposes. ineffective to. translate its signal to its output circuit. I when the control potential has a larger value at which the switching stage It is eflective to translate its signal from its input circuit terminals 21, 28 to its output circuit terminals 29, 30,

the signal voltages developed across the resistors '6! "of the switching stages l3 and I4, in the manner previously described in connection .with the switching stage IJ'Q-prevent the switching stages l2 and I4 from being eflective to .45 translate the signals individually applied thereto. It will thus be seen that the'switching stages of-this arrangement are only responsive to individual amplitude values oi the control potential selectively to translate the signals individually .50 applied thereto from the input circuit to the output circuit associated therewith.

.The Fig. 6 modification of the invention is essentially similar to that of Fig. 5, similar circuit elements being designated by similar reference numerals, except that apair of rectifier devices 83, i4 replaces each of the vacuum tubes I8 01' the Fig.- 5 arrangement. In the present arrangement, the input circuit terminal 22 01' the electronic switch I0" is directly connected through so theseries resistors and BI of each stage I4" and I!" to the output circuit terminal 29 thereof. The rectifier devices 63, 64 are connected with opposite polarities, that is, with the anode -of one rectifier device connected to the :65 cathodeof the other rectifier device, and are included in a series circuit between the Junction of the resistors 60', SI and ground, this series circuit including the biasing battery 25.

- A small biasing source comprising "a battery ---7.0 65 oi approximately 1.5 volts'potential isconnested in series betweenv the rectifier device 63 and the battery 25 and has a polarity to bias the anode of the rectifier'device 63 negative with respect to its cathode 'for a presently to be considered. A. similar biasing source comprisnals a, 10.1 This value or control potential is as cathode associated therewith, with the result 11 12 ing a battery 66 is similarly connected between, means individual to the stages for controlling the the rectifier device 64 and the battery 25. conductance characteristic of each stage thereof Considering now the operation of the Fig. 6 to render each of the stages only responsive to modification of the invention, assume that the individual amplitude ranges of the signal input control potential applied to the input circuit terselectively to translate the portion of the signal minals 22, 23 of the electronic switch I!" has input lying within said amplitude ranges.' a given small potential, for example zero poten- Also irom the above description of the invential. The battery 25 under the conditions astion, it will be seen that a very versatile electronic sumed, causes the rectifier device 83 of each of switch is provided and onewhich is capable oi. these switching stages [3", l4, and I!" to be adaptation to many applications. The electronic conductive, the current flowing from the battery switch of the invention possesses the advantages 25 through th circuit external to the control cirof substantially instantaneous operation, accurate c'uit terminals 22, 23, or through resistance R, the and positive control of the selective-switching resistor 60, and the rectifier device 63. The recoperation, and provides an arrangement whereby tifier device 63 or each switching stage has 'relaone or more signals may be selectively or 1 mtively low conductance under such condition and taneously translated as desired to one or more the signal applied to the input'circuit terminals output circuits of the electronic switch. There 21, 28 of each such stage is thus caused to traverse the conductive rectifier device 63 and, conseswitch of the invention is relatively simple and quentlv, is not applied to the output circuit terinexpensive and may be built into a relatively minals 29, 30 of each stage. slnall and compact unit. I

Now assume that the control potential applied The term conductance characteristic" as used ,is the further advantage that the electronic.

to control circuit terminals 22, 23 has a higher in the claims p ed h r t is intended to devalue than that of the battery 25 of any of the note the transconductance of the switching st electronic switching stages. The control poten- 25 where t s factor is d tly important, a tial under these conditions causes the rectifier i t e Figs. 1 and 5 amusements, r the condevice 64 of each stage to become conductive, the ductflhce e Vacuum-tube Switching St e rectifier device 63 being rendered nonconductive, Where the latter is Predominantly important. as The signal applied to the input circuit terminals in l'Ihe 8- 6 nt. 21, 28 of each of the switching stages is thus 30 h e there have n d sc hat a e at again caused to traverse the conductive rectifier Present eonsidered to e the preferred embodidevice 64 and, consequently, is not applied to the ments of this invention, it will be'obvious to those outp t circuit terminals 29 3g of such as skilled in the art that various changes and modi- However, when the value of the control potential flcations y be m de therein Wi hout d pa is just equal to that of the battery 25 of any of from the invention. and it is, thereiore, aimed in the switching stages i3", H" or ii", neither of the pp nded claims to cover all such changes the rectifier devices a: or as of that stage is renm modifications s ll within the true spirit dered conductive by the control potential and the and score of the invention battery 25. Under this condition, the batteries What s a ed is: 65 and 66 cause the rectifier devices 63 and 64 to 40 An electronic Switeh p i i a pl rality be nonconductive over a small range of approxiof vacuum-tube switching stages each includin mately 1.5 volts, whereby neither device is rein "an output circuit at which a signal translated dered conductive b the small amplitude signal y t stss is d v l p d. the nductance charapplied to the input circuit terminals 21. 2| 0! eeteristics f said stages dependin p fly' that stage. Consequently, this applied signal is the values of space currents of said vacuum tubes, repeated to its output circuit terminals as, so. a i n l inpu circuit for each of said stages. The resistors 60' in this arrangement are used as means for applying to each of said stages a signal isolating resistors to prevent the application of inp t h ving n f lv mpli e v ryin Ov r a signal or one of the switching stages,,when that a predetermined amplitude range, at least a porstage is translating the signal to its output cir- Of each Said Signal input circuits b61118 cult, from being applied to the output circuit tercommon to all of said stages, and means indiminals 2s, 30 of the other stages or the electronic e to said sta e for contr lli th n switch. ancecharacteristic of each stage thereof to render From the above description of the several modeach of said stag s e po s t individual P ifications of the invention, it will be evident that lions 9 said mplit e range of said signal inpu there is applied to the vacuum tube or tubes of selectively to translate the portions of said signal each switching stage an alternating signal poteninput ly wi hin a p r 8 amplitude tial and a unidi ti l tep-control potential range, said last-named means in at least one of sinc the e two ot ntial ar applied i cries said stages including means for rendering said one to the switching-stage vacuum tub or tube it so of said stages unresponsiveto all amplitude values will be seen that the alternating si nal potential of said input si nal different from the saidportlon is superimposed upon each step of the control of said amplitude range individual to said one 0! potential, whereby the same effect is produced Said sas though the amplitude of the alternating signal I An el tr ni swit h comprisin a plurality potential varied only over predetermined ampll- 01' vacuum-tube switching stages each in lu in tude ranges. Consequently, the transformers 2, an Output ir t at which a signal translated by 28 and the control circuit comprising control cirthe 815888 18 p d. the tl'flnmnductihM of cult terminals 22, 23 comprise means for applying said t s dependin primarily on chan es or to each of the stages a signal input having an the space currents of said vacuum tubes, a signal eilective amplitude varying over a predetermined input circuit for each or said stages, means for amplitude range, at least a portion of each of pplying to each oi said st es a s na inp h vthe signal input circuits being common to all ing-an-efiective amplitude varying over avpredeof the stages. The batteries 25, the sources ot termlned-ampll rans rat l D n' screen potential +Sc, the sources of anode poeach or said signal input circuits being common tential +3, and the load resistors II comprise 76 to all or said stages and means individual toss-1d stages for controlling the transconductance char acteristic of each stage thereof to render each of said stages responsive-to individual portions of said amplitude range of said signal'input, selectively to translate the portions of said signal input lying within said portions oi. said amplitude range,

.said last-named means in at least one of said stages including means for, rendering said one oi said stages unresponsive to all amplitude values of said input signal diflerent from the said portion '-'responsive' to one individual amplitude range or said control potential. selectively to translate said of said amplitude range individual to said one oi said stages.

3. An electronic switch comprising, a'p'lurality applied signal from the input circuit to the output circuit associated therewith, said last-named means in at least one'oi said stages including. means for rendering said one oi'said stages unresponsive'to all amplitude values of said control potential diflerent from the said amplitude range individual to said one of said stages.

6. An electronic switch comprising, a plurality oi -vacuum-tube switching stages each including an input circuit having a circuit portion adapted to have applied thereto a signal and each includ of vacuum-tube switching stages each including at least one vacuum tube having a control electrade, a' screen electrode and an anode, an output circuit for each of said stages including a load impedance coupled to the anode of the vacuum tube thereof and adapted to have developed thereacross a signal translated by said each stage, a signal input circuit for each ofsaid stages, means for applying to each of said stages a signal input having an eiiective amplitude varying over a predetermined amplitude range, at least a portion oi. each of said signal input circuits being common to all of said stages, means for biasing each of said screen electrodes and each of saidcontrol electrodes to predetermined operating biases, the values or said operating biases and the values of said load impedancesbeing proportioned to render each of said stages responsive only to in dividual portions of said amplitude range 01' said signal input, selectively to translate the portions of said signal input lying within said portions of said amplitude range.

4.- An electronic switch comprising, a plurality ing an output circuit at which said signal is de-- veloped after translation through said each stage, the conductance characteristics or said stages depending primarily on the values of space cur-' rents of said vacuum tubes, another circuit portion of said input circuits being common to all of fsaid stages and being adapted to have applied thereto a control potential having selectivelyvariable amplitude values, and means for indiof vacuum-tube switching stages each including an input circuit having a circuit portion adapted to have applied thereto a signal and each including an output circuit at which said signal is developed after translation through said each stage, the conductance characteristics of said stages depending primarily on the values of space currents of said vacuum tubes, another circuit portion of said input circuit being common to all oil said stages and being adapted to have applied thereto a control potential having selectively-variable amplitude values, and meansindividual to said stages 'for controlling the conductance characteristic of each thereof to render each of said stages responsive to at least individual amplitude values of said control potential, selectively to translate said applied signals from the inputcircult to the output circuit associated therewith, said last-named means in at least one of said stages including means for rendering said one of said stages unresponsive to all amplitude values of said control potential different from the said amplitude value individual to said one of said stages.

5. An electronic switch comprising, a plurality of vacuum-tube switching stages each including an input circuit having a circuit portion adapted to have applied thereto a signal and each including an output circuit at which said signal is developed after translation through said each stage,

the conductance characteristics oi. said stages depending primarily on the values of space currents of said vacuum tubes, another circuit portion of said input circuit being common to all of said stages and being adapted to have applied thereto a control potential having selectively-variable amplitude ranges, and means individual to said stages for controlling-the conductance characteristic of each thereof to render each of said stages vidually fixedly biasing each of said stagesto control the conductance characteristic thereof to render each of said stages responsive to at least individual amplitude values of said control potential, selectively to translate said applied signals from the input circuit to the output circuit associated therewith, said last-named means in at least one of said stages including means for rendering said one of said stages unresponsive to all amplitude values of said control potential ditierent from the said amplitude value individual to saidone of said stages.

being adapted to have applied thereto a control potential having selectively-variable amplitude values, means individual to said-stages for imparting to each of said stages a relatively high transconductance when said control potential has an individual amplitude value and relatively low transconductance for other amplitude values thereof to render each of said stages responsive only'to an individual amplitude value of said control potential, selectively to translate said applied signals from the input circuit to the ou tput circuit associated therewith.

8. An electronic switch comprising, a plurality of switching stages each including at least one vacuum tube having a control electrode and an an input circuit coupled thereto, each of said input circuits having one portion individual to the switching stage associated therewith and adapted to have applied thereto a signal and another portlon common to all of said switching stages and adapted to have applied thereto a control potential having selectively-variable amplitude values, an output circuit for each of said stages at which the signal individual to said each stage is developed after translation therethrough, and '70 means individual to said stages for rendering each of said stages responsive to at least individual amplitude values of said control potential, selectively to translate said applied signals from the input circuit to the output circuit associated therewith, said last-named means in at least one of vacuum-tube switching stages each includ ng.

an input circuit having a circuit portion adapted to have applied thereto a signal and each includingan output circuit at which said signal is developed after translation through said each stage, the conductance characteristics of said stages depending primarily on the values of space currents of said vacuum tubes, another circuit portion of said input circuits being common to all of said stages and being adapted'to have applied thereto a control potential having selectivelyvariable amplitude values, a source of operating bias included in each of the individual circuit portions of said input circuit, the values of said operating biases being proportioned to render each of said stages responsive to at least individual amplitude values of said control potential, selectively to translate said applied signal from the input circuit to the output circuit associated therewith, and the values of said operating biases in at least one of said stages being further proportioned to render said one of said stages unresponsive to all amplitude values of said control potential difierent from the said amplitude value individual to said one of said stages.

10. An electronic switch comprising, a plurality of switching stages each including at least one vacuum tube having a control electrode and an anode, an input circuit coupled to each said control electrodes and having a circuit portion individual to said stages, each of said individual circuit portions being adapted to have applied thereto a signal, an output circuit including a load impedance coupled to each of said anodes and adapted to have said signal developed thereacross after translation through said each stage, the conductance characteristics of said stages depending primarily on the values ofspace currents of said vacuum tubes, another circuit portion of said input circuits being common to all of said control electrodes and being adapted to have applied thereto a control potential having selectively-variable amplitude values, and means included in each of the individual circuit portions of said input circuit for biasing said control electrodes to a predetermined operating bias, the values of the operating biases and the values of said load impedances being proportioned to render each of said stages responsive to at least individual amplitude values of said control potential, selectively to translate said applied signals from the input circuit to the output circuit associated therewith, said last-named means in at least one of said stages including means for rendering said one of said stages unresponsive to all amplitude values of said control potential difierent from the said amplitude value individual to said one of said stages.

11. An electronic switch comprising, a plurality of switching stages each including at least one vacuum tube having a control electrode, a screen electrode and an anode, an input circuit coupled to each of said control electrodes and having a circuit portion individual to said stages, said individual circuit portions being each adapted to have applied thereto a signal, an outputcircuit I veloped thereacross after translation through said each stage, means for biasing each of said screen electrodes to ya predetermined operating bias, means included in each of the individual circuit portions of said input circuit for biasing said control electrodes to predetermined operating biases, another circuit portion of said input circuits being common to all of said stages and he adapted to have applied thereto a control potential having selectively-variable amplitudevalues, the values of the operating biases and the values of said load impedances being proportioned to render each 0! said stages responsive to at least individual amplitude values'of said control potential, selectively to translate said applied signal from the input circuit to the output circult associated therewith.

12. An electronic switch comprising, a plurality oi vacuum-tube switching stages each including an input circuit having a circuit portion common to all of said stages and a circuit portion individual to said each stage and adapted to have applied thereto a signal, an output circuit for each of said stages at which the signal individual to said each stage is developed after translation therethrough, the conductance characteristics of said stages depending primarily on the values of space currents of said vacuum tubes,;meansfor generating and applying to said common circuit portion of said input circuits a control potential the amplitude values of which increase by successive steps, and means individual to said stages for controlling the conductance characteristic of each thereof to render each of saidstages responsive to at least individual'amplitude values of said control potential, selectively and successively to translate said applied signals from the input circuit to the output circuit associated therewith, said last-named means in at least one oi. said stages including means for rendering said one of said stages unresponsive to all amplitude values of said control potential difierent from the said amplitude value individual to said one of said stages.

13. An electronic switch comprising, a plurality of vacuum-tube switching stages each including an input circuit having a circuit portion common to all of said stages and a circuit portion individual to said each stage and adapted to have applied thereto a signal, an output circuit for each of said stages at which the signal individuai to said each stage is developed after translation therethrough, the conductance characteristics of said stages depending primarily on the values of space currents of said vacuum tubes, means for generating and applying to said common circuit portion of said input circuit a periodic control potential the amplitude values of which increase during a recurrent period thereof by successive steps, and means individual to said stages for controlling the conductance characteristic of each thereof to render each of said stages responsive to at least individual amplitude values or said control potential, selectively and successively during recurrent periods to translate said applied signals from the input circuit to the output circuit associated therewith, said last-named means in at least one of said stages including means for rendering said one of said stages unresponsive to all amplitude values .01 said control potential different from the said amplitude value individual to said one of said stages.

Jonn r. rsanruc'rou. 

